【Java】XML解析之SAX

SAX介绍

　　SAX(Simple API for XML)是一种事件驱动的流式XML文件处理方式，区别与DOM方式的是不需要在内存中建一棵DOM树，而是根据读取XML时遇到的标签事件来顺序处理，因此具有速度快，内存占用上的优点。

XML生成

　　代码如下：

　　

 package com.test.sax;

 import javax.xml.transform.OutputKeys;
 import javax.xml.transform.Result;
 import javax.xml.transform.Transformer;
 import javax.xml.transform.TransformerConfigurationException;
 import javax.xml.transform.sax.SAXTransformerFactory;
 import javax.xml.transform.sax.TransformerHandler;
 import javax.xml.transform.stream.StreamResult;

 import org.xml.sax.SAXException;
 import org.xml.sax.helpers.AttributesImpl;

 public class TestCreateXml {

     public static void main(String[] args) {
         //创建SAXTransformerFactory实例
         SAXTransformerFactory factory = (SAXTransformerFactory) SAXTransformerFactory.newInstance();
         try {
             //创建TransformerHandler实例
             TransformerHandler handler = factory.newTransformerHandler();
             //创建Transformer实例
             Transformer transformer = handler.getTransformer();
             //设置输出的xml属性，encoding为编码，
             transformer.setOutputProperty(OutputKeys.ENCODING, "UTF-8");
             //indent是确保输出的xml文件能够自动换行
             transformer.setOutputProperty(OutputKeys.INDENT, "yes");

             //创建Result对象，将Result对象加载到TransHandler中
             // 注意：1、这一步必须在Transformer.setOutputProperty()之后，不然设置的xml属性将不生效
             // 2、这一步也必须在TransformerHandler.startDocument()之前，不然会报错。
             // 分析源码后发现，startDocument()会先判断result是否为空，为空则报错
             Result result = new StreamResult("src/test-sax-create.xml");
             handler.setResult(result);

             // 创建属性Attribute对象
             AttributesImpl attr = new AttributesImpl();
             //开始写文件
             handler.startDocument();
             //写入根节点conpany
             handler.startElement("", "", "conpany", attr);

             //清空属性，
             attr.clear();
             //设置属性
             attr.addAttribute( "", "", "name", "", "1");
             //写入根节点的子节点book
             handler.startElement("", "", "department", attr);

             attr.clear();
             //分别写入book节点的子节点
             attr.addAttribute( "", "", "name", "", "employee1");
             attr.addAttribute( "", "", "id", "", "1");
             handler.startElement("", "", "employee", attr);
             //写入子节点内容
             handler.characters("123".toCharArray(), 0, "123".toCharArray().length);
             //写入子节点末尾
             handler.endElement("", "", "employee");
             //写入department节点末尾
             handler.endElement("", "", "department");
             //写入根节点末尾
             handler.endElement("", "", "conpany");
             //写文件结束
             handler.endDocument();
         } catch (TransformerConfigurationException e) {
             e.printStackTrace();
         } catch (SAXException e) {
             e.printStackTrace();
         }
     }
 }

生成文件如下：

　　

XML解析

　　代码如下：

　　

 package com.test.sax;

 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;

 import javax.xml.parsers.ParserConfigurationException;
 import javax.xml.parsers.SAXParser;
 import javax.xml.parsers.SAXParserFactory;

 import org.xml.sax.Attributes;
 import org.xml.sax.SAXException;
 import org.xml.sax.helpers.DefaultHandler;

 public class TestParseXml {

     public static void main(String[] args) throws SAXException, IOException, ParserConfigurationException {
         //创建SAXTransformerFactory实例
         SAXParserFactory saxParserFactory = SAXParserFactory.newInstance();
         //创建TransformerHandler实例
         SAXParser saxParser = saxParserFactory.newSAXParser();

         MyHandler myHandler = new MyHandler();

         saxParser.parse(TestParseXml.class.getClassLoader().getResourceAsStream("test.xml"), myHandler);
     }

 }

 class MyHandler extends DefaultHandler{

     /**
      * 开始解析文档时，调用的方法
      */
     @Override
     public void startDocument() throws SAXException {
         System.out.println("---------startDocument-------");
     }

     /**
      * 文档解析完结时，调用的方法
      */
     @Override
     public void endDocument() throws SAXException {
         System.out.println("---------endDocument-------");
         super.endDocument();
     }

     /**
      * 开始解析每个元素时，调用的方法，会重复调用
      */
     @Override
     public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {

         //qName 元素标签
         System.out.println("---------startElement-------" + qName);

         // 处理属性
         if(attributes != null )
         {
             for (int i = 0; i < attributes.getLength(); ++i)
             {
                 String attrName = attributes.getQName(i);
                 String attrValue = attributes.getValue(i);
                 System.out.print("\t "+ attrName +  "=" + attrValue);
             }
         }
         System.out.println("");
     }

     @Override
     public void endElement(String uri, String localName, String qName) throws SAXException {

         System.out.println("---------endElement-------" + qName);
     }

     /**
      * 解析到每个元素的内容时会调用此方法
      */
     @Override
     public void characters(char[] ch, int start, int length) throws SAXException {
         String content = new String(ch,start,length);
         System.out.println("---------characters-------" + "content == "+ content);
     }
 }

控制台输出：

　　

 ---------startDocument-------
 ---------startElement-------conpany
      name=hd
 ---------characters-------content ==   

 ---------startElement-------department
      name=department1
 ---------characters-------content ==   

 ---------startElement-------employee
      name=employee1     id=1
 ---------characters-------content == 123
 ---------endElement-------employee
 ---------characters-------content ==   

 ---------endElement-------department
 ---------characters-------content ==   

 ---------startElement-------department
      name=department2
 ---------characters-------content ==   

 ---------startElement-------employee
      name=employee2     id=2
 ---------characters-------content == 321
 ---------endElement-------employee
 ---------characters-------content ==     

 ---------startElement-------employee
      name=employee3     id=3
 ---------endElement-------employee
 ---------characters-------content ==     

 ---------endElement-------department
 ---------characters-------content ==   

 ---------startElement-------department
      name=department3
 ---------characters-------content ==   

 ---------endElement-------department
 ---------characters-------content ==   

 ---------endElement-------conpany
 ---------endDocument-------

Simple API for XML